It is well known that the efficiency of an electrical conductor assembly for tubular conductor pipe is primarily dependent upon the positiveness of the electrical and mechanical connection, between the ends of the inner conductor tubes within adjacent lengths of outer pipe, provided by internal interconnect couplers. Due to the electrical conductivity and sturdiness of the pipe and external couplers, it is readily apparent that the durability of the internal interconnect couplers is most critical since it is necessary to repeatedly break down and remake drill strings, such as when changing drill bits, and other similar pipe. Accordingly, the internal interconnect couplers must conduct electrical current between adjacent inner conductor tubes as well as electrically insulate and mechanically seal off the ends of said tubes from the contiguous inner surfaces of the end portions of external couplers of the outer conductor pipe.
Representative examples of the prior art include the following U.S. Pat. Nos.:
Polk--2,000,716 PA1 Crites et al--2,178,931 PA1 Lee--2,301,783 PA1 Feaster--2,531,120 PA1 Atkins--3,184,706 PA1 Brandt--3,253,245 PA1 Barry et al--3,829,816 PA1 Godbey--4,012,092
The internal interconnect coupler of my patent, supra, as well as other prior art disclosures are not completely satisfactory in that they are relatively fragile and/or of insufficient durability and sturdiness to withstand the aforesaid necessity of repeatedly breaking and remaking the tool joints of drill strings or external couplers of other tubular conductor pipe. It is noted, however, that the prior art couplers are sufficiently durable to function over extended periods of time if there is not excessive making and breaking or coupling and uncoupling of said tool joints, pipe or external couplers of said pipe.
In my patent, it is difficult to maintain a fluid tight seal between the ends of each inner electrical conductor tube and the contiguous pin and box ends of the pipe which may form an outer electrical conductor of an electrical coaxial assembly, particularly, about the lower or inner contact ring of the internal interconnect coupler. The elastic material of the annular packing element of the latter cannot be made of sufficient firmness to maintain its deformed shape and prevent displacement of said coupler. Initial unthreading as well as final threading of the pin and box pipe ends tends to rotate and displace this coupler from the box since only the frictional engagement of the packing element with the screwthreads of said box is provided for holding said coupler in place when the pipe is uncoupled. Also, the pressure exerted on the elastic packing element upon "making up" a tool joint or external coupler causes it to expand inwardly as well as outwardly and thereby reduce the internal diameter of the pipe. In addition, the electrical current carrying capacity of the interconnect coupler is limited by the diameter of the spring wire extending between and connecting the contact rings at the ends of said coupler, and this limiting resistance increases with the addition of each length of pipe and coupler.
As set forth in my patent, supra, the expired patent to Polk discloses an electrically insulated coaxial conductor assembly wherein the drill string is utilized as the outer electrical conductor and detachable electrically insulated helical springs are used as interconnect couplers between adjacent sections of the inner electrical conductor. This assembly, however, involves repeated engagement and disengagement of coaxial insulated parts and the likelihood of irreparable damaging due the rough handling encountered during coupling and uncoupling of drill pipe. In FIG. 2, a helical spring engages and electrically connects adjacent ends of inner tubular conductor sections which are electrically insulated from drill pipe by dielectric liners. In FIG. 3, the inner electrical conductor sections comprise insulated electrical wires or rods secured by tubular sheaths to metallic collars or sleeves mounted in the bore of drill pipe between adjacent inner conductor sections. Ends of wires or rods are electrically connected to ends of springs by annular rings. Fragile structure due to telescopic ends of liner sections.
In the expired patent to Crites et al, one or more insulated electrical conductors are mounted in exterior of tubing and each length of tubing has built up male and female joints at its ends with longitudinal openings therein for receiving the end portions of one or more coextensive electrical conductors sections. Each conductor section is insulated exteriorly and from the tubing by a tubular dielectric sleeve of substantially the same external diameter as the tubing joints. Electrical contacts are secured to the ends of each electrical conductor section and have complementary tapered surfaces exposed to the interior of each box or socket and the exterior of each pin so as to engage when the joints are coupled.
The expired Feaster patent discloses sections or lengths of pipe of novel (uncommon) construction, each having an exposed conduit for an electrical conductor extending longitudinally of and contiguous its bore. The ends of each conduit are embedded in the enlarged pin and box ends of the pipe for connection with an electrical contact pin and an electrical contact ring, respectively, embedded in the end faces of said pin and box. Flat interengaged faces of annular insulating bodies or rings, which surround the contact pin and contact ring, will not withstand any appreciable fluid pressures much less the relatively high pressured encountered in oil wells. Leakage between the insulating rings short circuits the electrical connection.
The expired Lee patent discloses an electrical circuit for each length of pipe comprising a plurality of exposed coextensive wires exposed to the well fluids and respectively connected at each end to screws which are embedded in annular insulating rings disposed within the male and female coupling members of the pipe and which are connected to embedded electrical contacts having outer end portions for respective engagement with one another. The exposed wires are most undesirable.
The coaxial cable connector of the patent to Atkins has an axial center conductor embedded in dielectric member which insulates it from outer tubular conductor enclosed in dielectric sheath or cable jacket. Discloses camming members having coacting tapered surfaces for deforming gaskets and crimping. No fluid conductor shown.
In the patent to Brandt, the drill string is employed as an outer electrical conductor and an electrical conduit extending longitudinally of each length of pipe forms the inner electrical conductor. An electrical cable, containing insulated wire, is disposed within each conduit and the ends of the wire are connected to electrical contact rings embedded in elastic collars and adapted to mate when pipe is coupled.
The Barry et al patent discloses an electrical coupling assembly having plug type connectors with coacting pins and sockets engageable and disengageable upon relative linear movement of pin and box members of coupling. Not useable with screwthreaded coupling members.